The present invention relates to an arrangement for gripping and holding or releasing material, such as material held and worked in a lathe chuck, this arrangement being referred to hereinafter as a gripping arrangement.
The invention is based on a gripping arrangement that includes a piston-cylinder assembly and a number of material gripping and holding or releasing elements, so-called gripping elements and illustrated in the form of so-called gripping claws. A gripping arrangement equipped with such gripping elements can be activated by axially-related movement of said piston-cylinder assembly so as to rotate the gripping elements around a body-related axis between two positions, a first and a second position, in which the gripping-elements and gripping-claws are open and closed respectively.
Piston-cylinder assemblies of this kind include a piston-part and a cylinder-part which are adapted to move axially and reciprocatingly relative to one another through the action of a pressurized medium and a spring arrangement or spring unit.
By xe2x80x9cpiston partxe2x80x9d is meant a piston-related arrangement where an outer peripheral surface, normally a cylindrical surface of circular cross-section, is machined to carry or present sealing means, such as packings, piston rings or the like against an inner surface of the cylinder part.
By xe2x80x9ccylinder partxe2x80x9d is meant a cylinder-related arrangement where an inner surface, normally a cylindrical surface of circular cross-section, that has been made smooth at least within a given area, so as to be able to co-act with the sealing means on said piston part.
Alternatively, the cylinder part may be fitted with sealing means and the piston-part made smooth, in accordance with the inventive concept.
In the case of known piston-cylinder assemblies, the cylinder-part is normally fixed in relation to a stand or frame and the piston-part is moved reciprocatingly in relation to the cylinder-part by a working medium that is pressurised in a pressure generating device.
Several different designs of gripping arrangements of the aforedescribed nature are known to the art.
The gripping arrangement illustrated and described in GB Patent Publication 966 644 is a particular example in this regard.
The construction taught by Patent Publication U.S. Pat. No. 2,381,657 is also relevant in this regard.
Swedish Patent Application 9200096-7 teaches a material gripping and holding or releasing arrangement which includes a piston-cylinder assembly having a number of material gripping and holding or releasing elements, so-called gripping claws.
These gripping claws are caused to pivot about a fixed shaft between two positions, an open position and a closed position, in response to axial movement of the piston-cylinder means.
In the case of these earlier known arrangements taught by the aforesaid prior publications where the gripping claws are actuated by a piston-cylinder means, the claws are moved in response to axial movement of the piston in a cylinder that is fixed in relation to a machine body.
The present invention can be considered to constitute a further development of the gripping arrangement described and illustrated in International Patent Application PCT/SE 95/01193 (having International Publication No. WO 96/12582) and reference is made to this publication for a closer understanding of the basic principles of the present invention.
When taking into consideration the technical deliberations that a person skilled in this particular art must make in order to provide a solution to one or more technical problems that he/she encounters, it will be seen that on the one hand it is necessary initially to realise the measures and/or the sequence of measures that must be undertaken to this end, and on the other hand to realise which means is/are required in solving one or more of said problems. On this basis, it will be evident that the technical problems listed below are highly relevant to the development of the present invention.
When considering the present state of the art; as described above, it will be seen that a technical problem resides in providing a gripping arrangement of the aforedescribed kind that is comprised entirely of only a few individual parts, and which can be readily assembled and readily dismantled and where its component parts can be readily exchanged when becoming worn and/or when changing a gripping arrangement of one shape and size for a gripping arrangement of another shape and size.
With respect to the use of a gripping arrangement that comprises only a few individual parts, a technical problem resides in realising the significance of and the advantages afforded by using as a first part a fixed piston-part, by using as a second part a reciprocatingly movable cylinder part, by using as a third part a central body-related shaft-part, by using as a fourth part a spring unit, and by using a number of fifth parts, such as three parts, in the form of gripping elements.
Another technical problem is one of realising the significance of and the advantages associated with a gripping arrangement of the aloredescribed kind which includes a simple piston-cylinder construction in which the cylinder-part is reciprocatingly movable in relation to its longitudinal axis, said reciprocating movement also being relative to a shaft-like body-related part and also relative to said piston-part, said shaft-like part and said piston-like part both being fixed in relation to a body part.
Another technical problem is one of realising the significance of providing the cylinder-part of said piston-cylinder means with a circumferentially extending groove adapted for co-action with the gripping-element arrangement and functioning particularly as a support for the rear support surfaces of the gripping elements or gripping claws, such as the rolling surfaces thereof.
Another technical problem is one of realising the significance of and the advantages afforded by using a specially formed, body-related and shaft-like central part that will slide through the cylinder-part and which is adapted to co-act with the piston-part and firmly hold said piston-part.
It will also be seen that a technical problem is one of realising the significance of and the advantages afforded by providing the body-related part within one end-part thereof, its front part, with a number of radially extending slots or grooves adapted to respective gripping-element arrangements, and with a hole and a shaft or pin extending transversely from the centre shaft, such as to pivotally hold respective gripping-element arrangements through the medium of a hole in the gripping element.
Another technical problem is one of creating conditions with the aid of constructive means such that when the gripping arrangement is assembled, each of said transverse holes and a shaft or pin accommodated therein, and requisite stop means, such as stop screws, can be accommodated in the cylinder part.
In order to facilitate removal of the gripping-element arrangement and the replacement of one arrangement with another, it will be seen that a technical problem remains in enabling the transverse hole and a shaft located therein to take a position in which they are completely free or preferably only partially free in a position immediately adjacent said cylinder part.
It will also be seen that a technical problem resides in providing a gripping arrangement in which the retracted position of the gripping-element arrangements and an adapted immediately external position can be achieved solely by rotating the cylinder-part around the piston-part through a predetermined number of turns, such as three to four turns.
Another technical problem is one of realising the conditions required with respect to dimensioning of the depth of a groove in the cylinder-part so as to enable parts of the gripping-element arrangements to be brought to an exposed position immediately outside the cylinder-part.
Another technical problem is one of realising the significance of and the advantages afforded by allowing a part of a fixed body to function as the piston-part.
Yet another technical problem is one of realising the significance of and the advantages afforded by allowing the cylinder-part to move reciprocatingly in its axial direction relative to said body (a body-associated central part and the piston-part) through the medium of a movement activatable device.
Another technical problem is one of enabling the gripping edges of the readily assembled and readily dismantled gripping-element arrangement to take a first position (an open position) when the piston-part is fully retracted relative to the cylinder-part, and to take a second position (a closed position) when the piston-part has been fully extended relative to the cylinder-part by means of a pressurised medium, such as coolant, and to enable the rear parts of the gripping-element arrangement to turn in an arcuate path around their attachment point, said arcuate path being symmetrical with or at least generally symmetrical with a vertical plane through the pivotal attachment point.
In the case of this application of the invention, a technical problem resides in realising the significance of and the advantages afforded by providing respective gripping elements with a first and a second end-part where one end-part has the form of a gripping claw that includes a material gripping surface or gripping edge, and the other of said end-parts is firmly connected to and readily releasable from said central part through the medium of a pivot shaft.
Another technical problem is one of realizing the significance of causing said body-associated or body-related central part to extend through the cylinder-part and through the piston-part, and of providing the forward portion of the central-part with an adapted number of elements for rotatable co-action with one end of respective gripping-element arrangements, and by providing, at the rear portion of said gripping elements, roller bearing for facilitating rotary movement of the gripping elements along radially extending support surfaces formed transversely of a circular groove provided in the cylinder-part, in response to axial movement of the cylinder-part in relation to the piston-part.
Another technical problem is one of realising the significance of allowing the body-related central part to be comprised of a cylinder-shaped part whose front end-part includes said elements and radial grooves in a collar for accommodating said gripping-element arrangement and for co-action with one end of respective gripping elements and the rear, tapering part of which is firmly connected to the body and adapted to hold the piston-part through the medium of an axially-related clamping action.
Another technical problem is one of realising the significance of and the advantages associated with adapting the rear region of a gripping element for radial co-action with and along a support surface belonging to the groove in the cylinder-part, within a region located between 25 and 75% of the distance between a centre line of the central-part and the peripheral cylindrical surface of said cylinder-part.
Another technical problem is one of realising the significance of providing such a gripping arrangement with a spring unit within and along the centre region of said central-part and enabling the spring unit, when fitted, to exert a pressure between a front collar or shoulder on the central-part and an inner edge of the cylinder-part.
Another technical problem is one of being able to realise the significance of providing the reciprocatingly movable cylinder-part with a peripheral collar or hollow-cylindrical part whose inner surface sealingly embraces the outer surface of the piston-part fixed relative to said body.
Another technical problem is one of realising the significance of and the advantages afforded by allowing each of a chosen number of radial grooves in said collar to open-out, via grooves in the cylinder-part, into said circular grooves in the outer cylindrical surface of the cylinder-part.
Another technical problem is one of realising the significance of providing in the rear portion of respective gripping elements a hole through which a shaft or pin extends and providing on said shaft and on each side of the gripping element roller bearings for rolling co-action with parts of the radially extending support surface of said circular groove.
Another technical problem resides in providing the outer part of the gripping element with a readily fitted and readily removed gripping member that can be easily produced from a mechanical/technical aspect.
Another technical problem is one of realizing the significance of giving the outer part of the gripping element a part-circular surface with which a part-circular on the gripping member can be connected.
Another technical is one of realizing the significance of giving the part-circular surface on the gripping element a purely circular shape that has an angle of arc greater than 90xc2x0, for instance between 120xc2x0 and 170xc2x0, while giving the gripping member a purely circular shape that has an angle of arc of between 90xc2x0 and 170xc2x0.
It will also be seen that a technical problem is one of realising the significance of providing a gripping-member locking device, such as a screw, adapted to the gripping element on a radial line passing through a part that is contained by the aforesaid angle of arc of the circular surface of the gripping member.
Another technical problem is one of realising the significance of positioning the locking device at an adapted distance from the gripping edge of the gripping member, for simple adaptation and attachment of the gripping member to said gripping element.
It will also be seen that a technical problem is one of providing a gripping element with a gripping surface, such as a slightly rounded surface, adapted for co-action with soft material, or of providing a gripping member with a knife-like gripping edge for gripping co-action with a harder material where said knife-like gripping edge can be readily replaced when worn down or when replacing the gripping-element arrangements with other gripping-element arrangements that are suitable for use in another material working operation.
Another technical problem is one of providing a gripping arrangement with which the gripping-element arrangement can be readily removed and/or replaced by adapted axial displacement of each of the pivot shafts within the body-related central part against means for stopping said axial movement.
With the intention of solving one or more of the aforesaid technical problems, the present invention takes as its starting point a gripping arrangement for gripping, holding or releasing material, such as material held and worked in a lathe chuck, wherein said gripping arrangement includes a piston-cylinder assembly and a plurality of material-gripping and material holding or releasing elements, a so-called gripping element arrangement, and wherein said gripping elements can be moved in an arcuate path between two positions, an open position and a closed position in response to axial movements generated by the piston-cylinder assembly.
In accordance with the invention, it is proposed that the cylinder-part of the piston-cylinder assembly shall be provided with a circumferentially extending groove which is able to function as a support for and co-act with support surfaces belonging to said gripping element arrangement.
According to proposed embodiments that lie within the scope of the inventive concept, it is proposed that a body-related central part shall extend through the cylinder-part and be adapted for fixed co-action with the piston-part.
One end-portion of the body-related central part will conveniently include radially extending slots or grooves adapted to respective gripping elements of said gripping element arrangement, with a hole and a pin or shaft received therein for pivotally securing said gripping-element arrangement.
It is also proposed that the piston-part also functions as a further body-related part.
Thus, the cylinder-part shall be reciprocatingly movable axially in relation to the piston-part in response to movement activatable means.
In a position in which the cylinder-part is forwardly moved in relation to the piston part, the gripping edges of the gripping elements of said gripping element arrangement are located in a first position (an open position), whereas said gripping edges of said gripping elements are located in a second position (a closed position) when the gripping elements are fully retracted.
The gripping elements of said gripping element arrangement shall each have a first and a second end-part, where the first end-part is in the shape of a claw having a material gripping surface or gripping edge, and the second end-part is firmly connected to said central-part through the medium of a pivot shaft, such as to be easily fitted and easily removed from said central part.
According to one embodiment of the invention, the body-related central part shall extend through the cylinder-part and through the piston-part, and the forward portion of said central part shall include means for pivotal co-action with one end of respective gripping elements, wherein roller bearings are provided in the rear region of the gripping element to facilitate movement along radially extending surface parts of the periphery-related groove orientated in the cylinder-part, during rotary movement of said gripping element in response to axial movement of said cylinder-part.
It is also proposed that the body-related central part is comprised of a cylindrical part whose front end-portion includes radial grooves in a collar for receiving said gripping element arrangement and for co-action with one end of respective gripping elements, and the rear-tapering part of which gripping element is firmly connected to the body and to the piston-part.
The invention also proposes that the rear region of the gripping element is adapted for co-action with a groove in the cylinder-part within a radial area that corresponds to between 25 and 75% of the radial distance between a centre line of the central-part and the outer peripheral surface of the cylinder-part.
A spring unit is arranged midway of the central-part and exerts a given pressure between a front collar on the central-part and the cylinder-part.
According to the invention, the cylinder-part will conveniently include an integrated, outer peripheral collar or a cylindrical hollow body which is adapted to surround the piston-part, which is fixed relative to the aforesaid body.
According to one embodiment of the invention, each of the radial grooves in the collar shall open out into the circular grooves in the outer cylindrical surface of the cylinder-part through corresponding radial grooves in said cylinder-part.
The rear end of respective gripping element arrangements include a shaft-accomodating hole. Mounted on the shaft and on each side of the gripping element are ball bearings which co-act with the radially facing support surfaces or parallel radially facing outer parts of the circular groove so as to roll along said surfaces or said parts.
According to another embodiment of the invention, the aforesaid body includes three slots which are spaced equidistantly at angles of 120xc2x0.
According to another embodiment of the invention, the gripping element arrangement is adapted to co-act with a separate gripping member which can be readily fitted to the outer part of respective gripping element and readily removed therefrom.
The gripping member can be easily manufactured from a technical aspect, preferably in a press or a lathe.
The outer part of the gripping element has an inwardly facing, part-circular or arcuate surface which can be coupled to an outwardly facing, part-circular or arcuate surface on the gripping member.
The circular surface on the gripping element may conveniently have a true part-circular shape with an angle of arc greater than 90xc2x0, preferably between 120xc2x0 and 170xc2x0.
The circular surface on the gripping member may also conveniently have a true part-circular shape, with an angle of arc of between 90xc2x0 and 170xc2x0.
For the purpose of enabling the gripping member to be secured to and released from said gripping element, the arrangement includes a locking device disposed on a radial line belonging to said circular shape and passing at least through the angle of arc of the circular surface on the gripping member.
The locking device is spaced at an adapted distance from a gripping edge of the gripping member.
The claw-like gripping edge of the actual gripping element is configured and adapted (rounded) to grip soft material, such as plastic and similar soft material, whose surface shall not be damaged.
A gripping edge on the separate gripping member is adapted (pointed) so as to be able to grip against harder material, such as steel and other metals.
Those advantages primarily associated with an inventive gripping arrangement reside in the provision of conditions which enable a complete gripping arrangement to be assembled from only a few parts, of which the gripping element arrangement can be readily replaced or exchanged.
The use of an axially reciprocatingly movable cylinder-part of a piston-cylinder assembly enables the gripping element arrangement to be easily withdrawn into the cylinder-part during operation, and projected out slightly when changing a gripping element arrangement.
The invention also enables a gripping member to be readily fastened to an outer part of the gripping element, said gripping member being a separate component and having a gripping edge and capable of being easily replaced with another gripping member in the event of excessive wear or in the event of an alteration in material-working conditions.